Our goal is to develop effective and safe cutaneous gene delivery for the therapy of skin disorders. Ongoing progress in molecular genetics has generated an array of potential molecular targets for the treatment of skin diseases. The inability to efficiently deliver corrective genes to involved tissue and cellular sites in vivo has precluded the development of effective gene therapies for these diseases. This proposal begins to address this need by focusing on increasing both the level and the duration of expression of genes delivered by cutaneous administration of plasmid DNA, using recent advances in gene transfer techniques. The goal of our proposed studies is: a) to develop maximally efficient cutaneous gene transfer; and b) to use this optimal gene delivery approach to demonstrate a measurable therapeutic endpoint in an appropriate animal model system. Our specific aims are: Aim 1. To maximize the level and duration of cutaneous gene transfer. We will examine the utility of a novel, long-expressing plasmid vector, a novel cationic polymer, and multiple dosing schedules in producing maximally efficient cutaneous gene transfer. We will examine skin gene transfer using both intradermal and topical routes of administration. We will also examine site-specific gene transfer into the skin by the use of keratinocyte-specific promoter elements. Specifically, we will assess: a) Expression plasmid design. We will examine the efficacy of a novel Epstein-Barr virus (EBV)-based plasmid that has resulted in significantly prolonged gene expression upon systemic gene transfer in mice to deliver the reporter genes luciferase and beta-galactosidase to the skin of mice. b) Cationic polymer formulation. Recent studies have shown that the use of novel PEI:DNA complexes has resulted in substantially increased levels of gene transfer upon systemic administration of reporter genes to mice. We will determine the impact of PEI-based gene transfer on the level of reporter gene expression in the skin of mice. c) Number and frequency of doses. We will determine the effects of dosing schedules of naked DNA or DNA:cationic polymer complexes on the level and duration of skin gene transfer. d) Gene transfer in the skin by the use of skin-specific promoter elements. We will investigate restriction of expression to the keratinocytic system by incorporating the keratin 14 promoter in the EBV-based expression plasmid. Aim 2. To use the optimal cutaneous gene transfer approach developed in Aim 1 to express a biologically relevant gene and examine its therapeutic effects. We will examine the over expression of the xeroderma pigmentosum C (XPC) gene to attempt to demonstrate that re-introduction of the transgene to a knockout mouse can benefit the host. We will determine whether efficient expression of the XPC gene in mice will alter the response to UV-mediated DNA damage.